The present invention relates to a textile machine and the control method thereof.
It is known that in textile machines, such as crochet machines for warp knitting workings, also referred to as crochet galloon looms, formation of the woven product takes place by mutual interlacing, following preestablished patterns, of a plurality of warp and weft yarns, suitably engaged by respective knitting members; said knitting members are for example needles mounted on a needle bar, eye-pointed needles supported by a guide bar and threading tubes mounted on one or more carrier slide bars.
These knitting members are operated by appropriate actuators, with synchronized cyclic movements, to cause mutual interlacing of the warp and weft yarns following the desired knitting pattern.
The weft and warp yarns are fed to the respective knitting members by a plurality of bobbins mounted on a rack-shaped structure called “unwinding creel”, or they are unwound from a drum called “beam”.
It is also provided that appropriate take-down rollers should cause sliding of the textile product and progressive supply of same to the machine exit.
The bobbins on which the weft yarns are wound are free to rotate about their longitudinal rotation axis, and the tension with which the weft yarns are fed to the carrier slide bar is determined by the rotation speed of the rollers that are interposed between the unwinding creel and the carrier slide bar and are disposed close to each other so as to engage the weft yarns.
Rotation of these rollers is usually caused by a kinematic connection between said rollers and the main shaft of the textile machine; since this connection is of a purely mechanical type, it keeps a fixed position during production of the whole fabric.
Therefore, irrespective of the amount of the longitudinal translations of each individual carrier slide bar (and of the related threading tubes), the amount of weft yarn supplied to each tube in the time unit is constant over the whole production cycle of the textile product. This means that each threading tube receives the same amount of weft yarn both when it is moved so as to jump over a single needle and when it jumps over several needles (e.g. 3-5 needles).
The kinematic connection between the main shaft and the rollers interposed between the unwinding creel and the carrier slide bar is obtained in such a manner that said rollers supply the threading tubes with an amount of yarn that is intermediate between the amount of yarn necessary to a threading tube when a minimum displacement thereof takes place and the required amount of yarn during the tube maximum displacement.
It is apparent that, taking into account the above described structure and the respective operation modalities, the fabric that is obtained will not be able to have excellent aesthetic features, since the same amounts of weft yarn are employed to make weft rows having different lengths from each other.
Likewise, the warp yarns too are fed to the guide bar through rollers disposed suitably close to each other, and the finished product is picked up from the front grooved bar by means of a quite similar roller member.
Both the feeding member of the warp yarns and the take-down member of the textile product are mechanically connected to the main shaft so that the follow-up ratio (i.e. the ratio between the number of revolutions carried out in the time unit by the feeding/take-down rollers and the number of revolutions carried out in the time unit by the main shaft) keeps constant over the whole working of the textile product.
Consequently, it is not possible to alter tensioning of the weft and warp yarns when supplied to the respective bars without stopping operation of the machine, neither is it possible to modify the pulling tension applied when the finished product is removed from the front grooved bar.
Therefore, by adopting these modalities of use of the loom it is not possible to alter the fabric compactness or density both in a transverse direction and in a direction parallel to the extension of the textile product, without stopping operation of the machine.
In addition, exactly due to the fact that the warp and weft yarns are fed to the eye-pointed needles and the threading tubes with a constant tension and the textile product is caused to slide between the take-down rollers with a constant tension in time it is not possible to obtain particular aesthetic effects through a controlled variation of the fabric compactness, without stopping operation of the machine, said aesthetic effects comprising alternations of thinner and more compact regions, narrowing or shrinkage of the textile product along a direction substantially perpendicular to the movement direction in which the textile product itself is moved by the take-down rollers, etc.